SPIDERS follows-up clusters of galaxies selected by cross-correlating faint ROSAT sources with red-galaxy excess found in SDSS imaging in the range 0.1<z>0.6. These are the most massive and largest clusters in the X-ray sky, and represent a well defined sample that can be used as a first stepping stone for cluster cosmology experiments via measurement of the growth of structure (with ~4,500 clusters, it will be by far the largest homogeneously X-ray selected sample with full spectroscopic followup).
In the first phase of the SPIDERS programme (a.k.a Tier-0), the targets are selected from the parent samples CODEX (Finoguenov et al. 2017) and X-CLASS (Clerc et al., 2012, Sadibekova et al. 2014), constructed on RASS and XMM-Newton archival observations respectively.
Once eROSITA data will become available, we will be able to target additional about 1,500 fainter, less massive and at higher redshift clusters. The better angular resolution of eROSITA over ROSAT, and the better energy resolution, implies we will be able to better characterize the X-ray/optical selection and provide competitive cosmological measurements of cosmic growth.
The sky distribution of SPIDERS_RASS_CLUS targets in equatorial coordinates. Each dot represents a red-sequence galaxy attached to a CODEX (X-ray detected) galaxy cluster. The color-code indicates the photometric redshift of the considered system. The insets highlight the levels of source clustering: there is about 1 CODEX galaxy cluster per square degree and galaxies in a system are clustered at the sub-arcmin scale.
Acknowledgements: please cite this page and Clerc et al., 2016 if you use these data products
